Balancing of centrifugal pumps.



P. A. PETERSON.

BALANCING 0F CENTRIFUGALPUMPS.

APPLICATION FILED AUG.I2. 1913.

1,1 5 1 ,964. Y Patented Aug. 31, 1915.

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9 a /0 9 M /6 /5 6 W ZR gvlugewtoz M v I AAQ/M M I w en sr TEs PATENT om-m PER ARVID PETERSON,- F TR-Enron, NEW JERSEY, ASSIGNOE'TO DE LAvAL STEAM TURBINE COMPANY, or TRENTON, NEW JERs Y, AooRroRAT oNoE NEW JERsEY.

BALANCING OE CENTEIFUGAL PUMPS.

' To (ZZZ whom it mad] concern:

Be it known that I, PER ARVID PETE SON, a subject .of the King of Sweden, and a resident of Trenton, in the county of Mercer and State of New Jersey, have invented certain anew and useful Improvements in Balancing making the provision of thrust bearing unnecessary. 7

The objects of my invention are to maintain the impellers of centrifugal pumps in perfect balance at all times, to avoid the use of thrust bearings, to reduce wear and leakage in suchpumps to a minimum, and to simplify the construction of such pumps.

I will now proceed todescribe my invention with reference to the accompanying drawings, and will then point out the novel features in claims.

In the drawings: Figure 1 shows a fragmentary axial section of a single stage centrifugal'pump embodying my invention, and Fig. 2 shows a similar section of a multistage centrifugal pump embodying my invention. 1

Referring first to Fig. 1, 1 designates the casing of a centrifugal pump, 2 the impeller shaft of such pump, 8 an impeller mounted on suchshaft, 4 the usual admission duct and 5 the usual discharge chamber.-.The impeller is provided with the usual passages 6, receiving liquid from the admission duct 4 and discharging into the space 7 and thence into the discharge duct 5. In rear of the impeller there is, as customary, a balancing chamber 8. On the inlet side of the impeller I have indicated the usual labyrinthinepacking comprising a stationary labyrinthine ring 9 and a rotating labyrinthine ring 10, the latter mounted upon the impeller and rotating with it; the two rings, 9 and 10, having intermeshing flanges providing a labyrinthine passage in the usual Specification of Letters Patent.

Patented Aug. 31', 1915. Application filed August 12, 1913. Serial No. 784,432.

manner. At the rear of the impeller I have indicated other labyrinthine rings, 11 and 12, ring 11 being stationary and ring 12 be'-' ing mounted upon and rotating with the im .peller; these rings 11 and 12 likewise having pumps; for according to former practiceit has been common; for the stationary. impeller ring on the rear side of the impeller to have its flanges facing toward the impeller; and correspondingly, accordingto former practice, the rotatinglabyrinthine ring-on the rear side of the impeller has had its flanges facing from the impeller; whereas just the reverse istrue of the construction herein illustrated and described. 'The impeller shaft is allowed slight play for longitudinal motion; which movement will reduce or increase, as the case may be, the distance between the ends of the flanges 13 of ring 12 and the ends of the corresponding grooves of ring 11, and will correspondingly decrease or increase, as the case may be, the distance between the ends of the flanges 14 of the stationary ring 11, and the ends of the corresponding grooves in ring 12. Of

course as thedistance between the ends of flanges 13 and 14 and the ends of the corresponding grooves increase, the distance between the flanges 15 of the ring 10 and the ends of the grooves of the ring 9, will increase,'and vice versa. In theoperation of thispump, since the pressure at 7 is nece ,sarily greater than the pressure at 4, whi e the pump is in operation,.there is a tendency for leakage from space 7 between rings 9 and 10 back into the inlet Land a corresponding tendency for leakage from space 7 between rings 11 and 12 back into balancing chamber 8; and this latter leakage, if no vent were provided from chamber 8, would lead to a pressure in chamber 8 edual to that in space 7; therefore I provide a duct 16 connecting the balancing chamber 8 with the inlet portion of the passages 6 of the impeller.

It will be seen that in the constructmn l with resulting building up of pressure in' balancing chamber 8 suflicient to restore shown-if there be an excess of thrust toward the. right the impeller will move slightly to the right, increasing the distance between the. flanges of rings '12 and 11 and the ends of the grooves in which those" flanges are located, and so permitting 1ncreased flow between the rings 12 and 11,

equality of thrust in both directions; conversely,-if the thrust toward the left be greater than the thrust toward the right, the

, impeller will move slightly to the left, de-

creasing the distance between the ends of the flanges of the rings 11 and 12, and the ends of the grooves in which those rings are located, with resulting decrease offlow between rings 11 and 12, and therefore resulting decrease of pressure in balancing chamber 8. 7

Heretofore, in centrifugal pumps pro vided with labyrinthine packing. it has been common to employ a balancing duct, similar to duct 16, connecting the balancing chamber in rear of the impeller with the inlet] portion of theimpeller; and since the area of cross section of the balancing duct or ducts. 16 must be proportionate to the leakage between the labyrinthine packing rings, and since these labyrinthine rings are necessarily subjected to wear with consequent increase of leakage (in the former constructions wherein radial clearance between the rings has been provided), it has been necessary at frequent intervals, as the radial clearance between the labyrinthine packing rings increases from wear, to renew these rings as otherwise the thrust may increase to a dangerous extent and also decrease the capacity and efiiciency of the pump to a material extent. According tomy invention I reduce the radial clearance between the intermeshing labyrinthine rings to the lowest amount consistent with good running, and reasonable ease'of fit, and instead provide end clearance between the ends of the. flanges of the labyrinthine rings, and the ends of the grooves in which such rings are located; which end clearance varies according to the position'assumed by the impeller at any instant. Since, according to my invention, the throttling action in the labyrinthine rings by means of which the automatic balancing of the pump is effected, occurs mainly between the ends of the flanges of the labyrinthine rings and the ends of the grooves in which such flanges run, wear of these'flanges has very little eflect on the leakage between these rings, since the impeller automatically assumes a position whereby the leakage is regulated to give the required pressure in balancing chamber 8, and therefore in practice renewal of the labyrinthine packing rings is very seldom required. It also follows, from my invention, that the smaller be the area of cross section of the balancing duct or ducts 16, the smaller is the leakage which can be taken care of by these ducts and consequently a smaller axial clearance will be established automatically between the ends of the flanges of rings 12] and 11 and the ends of the grooves in which such flanges run, Of course, there is'a minimum permissible clearance between the ends of these flanges and the ends of the grooves-in which they run, which minimum clearance may vary under different conditions of use; and the area of the balancing duct or ducts 16 should be proportioned in the design of the pump, to give that minimum axial clearance of the flanges of the labyrinthine rings 11 and 12 which the conditions of use require In Fig. 2 I have illustrated my invention as applied to a two stage centrifugal pump. It will be obvious that the number of stages of such pump might be greater than shown. The construction is in general the same as inFig. 1 except that labyrinthine packing rings 17 and 18 are provided between the stages of the pump to reduce to a minimum back flow between stages, these rings being so arranged that they control the extent of leakage in the same manner as rings 11 and 12.

In a companion application, filed August.

-ancing duct, extending from the balancing chamber in rear of the impeller,to the admission duct of the casing, and except that in the multistage pump shown in my said companion application labyrinthine packing between the stages is not provided, and in such multistage pump of my companion application, the balancing duct extends from the balancing chamber in rear of the last impeller to the admission duct of the casing in front of the first impeller; whereas in the structure, of my present application, a bal: ancing duct 16 is provided in each impeller. The construction of thispresent case is pref erable, in multistage pumps, designed for very high pressures, and the construction in multistage pumps of my said application filed August 12, 1913,81; No. 784,433, is preferable for moderate pressures;

' I am aware that the automatic balancing as to end thrust of the impellers of single stageand multistage pumps has been proposed heretofore; but so far-as I know, this,

application, and my said companion application, filed August 12, 1913, Sr. No. 7 84,433,

' are the first instances of automaticbalancin obtained'by' throttling action between the ends of flanges of labyrinthine packing rings and the, ends of grooves, in which such flanges work, regulated by automatic axial motion of the impeller. I

The'claims generic to the structure shown in this present application, and in my said companion application filed August12, 1913,

' Sr. No. 784,433, will be found inthe said companion application.

It will be noted that m the constructions shown in this application, the impeller labyrinthine packing ring or' rings 12 on the rear side or sides of the impeller or impellers is or are of the same diameter as the ring or rings 10 on the inlet side of the im--- peller or impellers. In my said companion application filed August-12, 1913, Sr .jNo.

7 84,433, I illustrate a construction involving the use of automatically adjusted throttling means for regulating flow of liquid out of the balancing chamber 8; and the use of such automatically adjusted throttling means permits the impeller labyrinthine packing ring or v rings on the rear side or sides of the impeller -or impellers to be made of larger diameter than the impeller labyrinthine packing ring.

or rings on the inlet side of the impeller or impellers, which is often advantageous. In

the construction shown herein, since no such throttling means is employed, the suction pressure'of each impeller should exist. in

the balancing chamber 8 of that impeller, in

order that the-impeller may operate in balance; and inthe construction shown herein, such will be the case, under anyoperating conditions as to head or capacity.

What I claim is: t 4 1. A centrifugal pump comprising in combin'a'tion a casing having a flow passage 7 1 within it-and an impeller withinsaidcas' ing mounted for slight axial motion therein as 'well as forrotary motion, and having a balancing chamber on the rear side of such impeller' and between the impeller and the casing, said impeller provided with a balancing; duct connecting .such balancing chamber with the inlet side of the impeller,

of means for controlling leakage from the flow passage of such casing to said balancingchamber comprising labyrinthine packing rings, one carried by the casing and the from each such balancing chamber, of

or decrease, as the case may be, of flow be- ;tween such labyrinthine rings. 7 3. A multistage centrifugal pumpcom- -duct and outlet duct communicating with other by the impeller, and one provided 5 with a cylindrical flange and the other with a corresponding cylindrical groove adapted to receive such flange, there being end clearance between the end of such flange and the baseof suchgroo've, the working face of the impeller'labyrinthine ring facing that impeller, whereby axial movement of the 1mpell'er due tounbalanced thrust tends to restorebalance of thrust by increase or decrease, as the case may be, of the flow between such labyrinthine rings.

2. A. multistage centrifugal pump comprising 'a casing having a flow passage through it divided into stages, and an inlet duct and outlet duct communicating with such flow passage, a multistage impeller structurewithin' said casing comprising separate impellers for the several stages, there being abalancing chamber in rear of each impeller, and means for the escape of liquid the casing labyrinthine'ring facing toward the impeller, whereby axial movement of the impeller structure, due to unbalanced thrust tends to restore balance of thrust by increase prising a casing having a flow passage through it dlvided into stages, and an inlet such flow passage, a multistage impeller structure within said casing comprising separate impellers for the several stages, there being a balancing chamber in rear of each impeller and means for the escape of liquid from each such balancing chamber, of means for controlling leakage from the flow passage of such casing to said balancing chambers comprising labyrinthine packing rings 7 between each such balancing chamber and the flow passage, each such labyrinthine packing comprising two coacting labyrinthine r ngs, one carried by the casing and the other by the impeller, and one provided with a cylindricalfiange and the other with a corresponding cylindrical groove adapted to receive such flange, there being end clearance between the end ofsuch flange and the base of such groove, that side of each such specification in the presence of two subscribimpeller labyrinthine ring which coacts with ing witnesses.

the casin Iab rinthine rin facin toward .the impel l er, aid other laby inthing packing P ARVI'D PETERSON 5 between the balancing chamber of one stage Witnesses;

and the stage in advance. C. R. WALLER, In testimony whereof I have signed this GEO. BLPAGE. 

